Question: Solve for $x$ and $y$ using substitution. ${x-4y = -3}$ ${x = -2y+3}$
Solution: Since $x$ has already been solved for, substitute $-2y+3$ for $x$ in the first equation. ${(-2y+3)}{- 4y = -3}$ Simplify and solve for $y$ $-2y+3 - 4y = -3$ $-6y+3 = -3$ $-6y+3{-3} = -3{-3}$ $-6y = -6$ $\dfrac{-6y}{{-6}} = \dfrac{-6}{{-6}}$ ${y = 1}$ Now that you know ${y = 1}$ , plug it back into $\thinspace {x = -2y+3}\thinspace$ to find $x$ ${x = -2}{(1)}{ + 3}$ $x = -2 + 3$ ${x = 1}$ You can also plug ${y = 1}$ into $\thinspace {x-4y = -3}\thinspace$ and get the same answer for $x$ : ${x - 4}{(1)}{= -3}$ ${x = 1}$